Compact solid-state neutral particle analyzer in current mode

Zhu, Y. B.; Bortolon, A.; Heidbrink, W. W.; Celle, S. L.; Roquemore, A. L.

doi:10.1063/1.4732070

Cited by 23 publications

(21 citation statements)

References 20 publications

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“…14 Conditions with multiple unstable AEs occur both in L-mode plasmas during the current ramp 6,14,25 and in H-mode steady-state scenario plasmas with elevated q profiles. 26,27 Fast-ion diagnostics include the volume-averaged neutron rate, 28 which is dominated by beam-plasma reactions in the L-mode plasmas, FIDA diagnostics with oblique sightlines, 29 and solid-state neutral-particle analyzers (NPA) operated in current mode 30 (Fig. 2).…”

Section: Critical Gradient Behaviormentioning

confidence: 99%

Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

et al. 2017

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Experiments on the DIII-D tokamak have identified how multiple simultaneous Alfvén eigenmodes (AEs) lead to overlapping wave-particle resonances and stochastic fast-ion transport in fusion grade plasmas [C. S. Collins et al., Phys. Rev. Lett. 116, 095001 (2016)]. The behavior results in a sudden increase in fast-ion transport at a threshold that is well above the linear stability threshold for Alfvén instability. A novel beam modulation technique [W. W. Heidbrink et al., Nucl. Fusion 56, 112011 (2016)], in conjunction with an array of fast-ion diagnostics, probes the transport by measuring the fast-ion flux in different phase-space volumes. Well above the threshold, simulations that utilize the measured mode amplitudes and structures predict a hollow fast-ion profile that resembles the profile measured by fast-ion Dα spectroscopy; the modelling also successfully reproduces the temporal response of neutral-particle signals to beam modulation. The use of different modulated sources probes the details of phase-space transport by populating different regions in phase space and by altering the amplitude of the AEs. Both effects modulate the phase-space flows.

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Section: Critical Gradient Behaviormentioning

confidence: 99%

Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

et al. 2017

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“…In its present configuration, the solid-state NPA diagnostic is operated in the current mode. 18 The NPA and FIDA diagnostics considered here both view the 210RT neutral beam (Fig. 4).…”

Section: A Apparatusmentioning

confidence: 99%

“…The Main-ion and Tangential spectroscopic systems, 20 shown in red and orange respectively, provide a combined 20 midplane views of the neutral beam. The solid state NPA system (ssNPA), 18 shown in green, consists of three channels viewing the core region of the plasma from below the midplane.…”

Section: B Neutron Scintillator Orbit Weight Functionmentioning

confidence: 99%

Action-angle formulation of generalized, orbit-based, fast-ion diagnostic weight functions

Stagner

Heidbrink

2017

Physics of Plasmas

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Due to the usually complicated and anisotropic nature of the fast-ion distribution function, diagnostic velocity-space weight functions, which indicate the sensitivity of a diagnostic to different fast-ion velocities, are used to facilitate the analysis of experimental data. Additionally, when velocity-space weight functions are discretized, a linear equation relating the fast-ion density and the expected diagnostic signal is formed. In a technique known as velocity-space tomography, many measurements can be combined to create an ill-conditioned system of linear equations that can be solved using various computational methods. However, when velocity-space weight functions (which by definition ignore spatial dependencies) are used, velocity-space tomography is restricted, both by the accuracy of its forward model and also by the availability of spatially overlapping diagnostic measurements. In this work, we extend velocity-space weight functions to a full 6D generalized coordinate system and then show how to reduce them to a 3D orbit-space without loss of generality using an action-angle formulation. Furthermore, we show how diagnostic orbit-weight functions can be used to infer the full fast-ion distribution function, i.e., orbit tomography. In depth derivations of orbit weight functions for the neutron, neutral particle analyzer, and fast-ion D-α diagnostics are also shown.

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“…Recent development on compact solid state neutral particle analyzers (ssNPA) based on absolute extreme ultraviolet (AXUV) silicon photodiode 5 are very attractive because they are small in size, simple to operate, and low cost. [6][7][8][9][10][11][12] The full function integrated ssNPA system based on specially fabricated AXUV detectors with fast response and ultra-high vacuum (UHV) compatibility has been designed and installed for the first time on experimental advanced superconducting tokamak (EAST) in 2014, 6 based on the experience obtained from previous individual development such as advanced current mode operation on DIII-D, 7 coarse pulse height spectrum measurements on national spherical torus experiment (NSTX), 8,9 and other devices. [10][11][12] EAST, equipped now with two 50-80 keV 4 MW NBI and two 24-70 MHz 6 MW ICRH system, provides an excellent platform for EP study after recent significant upgrades.…”

Section: Introductionmentioning

confidence: 99%

First results from solid state neutral particle analyzer on experimental advanced superconducting tokamak

Zhang

Zhu

Zhao

et al. 2016

Review of Scientific Instruments

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Full function integrated, compact solid state neutral particle analyzers (ssNPA) based on absolute extreme ultraviolet silicon photodiode have been successfully implemented on the experimental advanced superconducting tokamak to measure energetic particle. The ssNPA system has been operated in advanced current mode with fast temporal and spatial resolution capabilities, with both active and passive charge exchange measurements. It is found that the ssNPA flux signals are increased substantially with neutral beam injection (NBI). The horizontal active array responds to modulated NBI beam promptly, while weaker change is presented on passive array. Compared to near-perpendicular beam, near-tangential beam brings more passive ssNPA flux and a broader profile, while no clear difference is observed on active ssNPA flux and its profile. Significantly enhanced intensities on some ssNPA channels have been observed during ion cyclotron resonant heating.

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Compact solid-state neutral particle analyzer in current mode

Cited by 23 publications

References 20 publications

Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

Fast-ion transport by Alfvén eigenmodes above a critical gradient threshold

Action-angle formulation of generalized, orbit-based, fast-ion diagnostic weight functions

First results from solid state neutral particle analyzer on experimental advanced superconducting tokamak

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